1985 460 trouble
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1985 460 trouble
The problem I am having with my 1985 460 motor in my f-350 is a rough idle and skip. I have already replaced distributor, electronic ignition, plugs, wires, cap and rotor.
I did a compression check on cylinders. #5,6,7, and 8 had 129-130. The plugs were a light tan. Plug 1 was 129-130, plug good (tan). #2 cylinder had reading of 135-140 and spark plug started to look wet. #3, plug was very wet and compression was 150. #4 looked ok, color tan and compression was 130.
I suspected exhaust valve or bent push rod but both seem to be ok.
I tested each cylinder and they are all getting spark. Number 3, though, does not seem to be firing. I just can't figure out why.
Anyone have any ideas what may make motor lope and skip, with some backfire when you back off on the gas?
Is there an easy way to check valve clearances on hydraulic lifters without using bleedown tool?
Available to me is a 460 4 barrel motor out of a 1977 Mercury. I was told I needed to change the oil pan and sump and it should fit without a lot of changes. Is this accurate?
Thanks, Jim
I did a compression check on cylinders. #5,6,7, and 8 had 129-130. The plugs were a light tan. Plug 1 was 129-130, plug good (tan). #2 cylinder had reading of 135-140 and spark plug started to look wet. #3, plug was very wet and compression was 150. #4 looked ok, color tan and compression was 130.
I suspected exhaust valve or bent push rod but both seem to be ok.
I tested each cylinder and they are all getting spark. Number 3, though, does not seem to be firing. I just can't figure out why.
Anyone have any ideas what may make motor lope and skip, with some backfire when you back off on the gas?
Is there an easy way to check valve clearances on hydraulic lifters without using bleedown tool?
Available to me is a 460 4 barrel motor out of a 1977 Mercury. I was told I needed to change the oil pan and sump and it should fit without a lot of changes. Is this accurate?
Thanks, Jim
Last edited by jimbo001; Nov 9, 2003 at 06:40 PM.
Senior User
Joined: Apr 2003
Posts: 126
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From: Alaska
To check valve clearances you can just use a heel bar and a piece of wire to bleed the lifter. Wrap the wire around the rocker arm and pry back on it with the heel bar. Make sure all the oil is bleed out. On my '83 460 allowable clearance was .075-.150 while desirable clearance was .100-.150. If you are getting good compression though I wouldn't think this was the problem. Not sure about the other 460. I have been told all you have to do is change pans also, but I rebuilt instead of swapping. Firing order and timing is OK huh?
Cross-Country
Joined: Oct 2003
Posts: 59
Likes: 3
From: Chesterfield, VA
doesn't sound like valves
Doesn't sound like a valve problem to me... You say that cylinder is actually higher than the others because of the extra oil/gas in that cylinder seating the rings nicely! My guess would be you have a bad plug/wire/distributor or possibly even a bad coil?
Lead Driver
Joined: May 2000
Posts: 9,236
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From: Senoia, GA
Re: doesn't sound like valves
Originally posted by rumblefish73
My guess would be you have a bad plug/wire/distributor or possibly even a bad coil?
My guess would be you have a bad plug/wire/distributor or possibly even a bad coil?
-jason-
Last edited by fishmanndotcom; Nov 10, 2003 at 11:43 AM.
Cross-Country
Joined: Oct 2003
Posts: 59
Likes: 3
From: Chesterfield, VA
wiped cam lobe?
Well if he has replaced all the wires, plugs, distributor, cap, rotor and the coil.... And is sure that the new parts he has bought aren't bad, as I have run across bad caps and bad wires out of the box....
Then, I would suspect a wiped intake cam lobe (hence the backfire when you let off the gas)...
hope this helps
if you fix it, let me know what you found... you got me wondering now...
jay
Then, I would suspect a wiped intake cam lobe (hence the backfire when you let off the gas)...
hope this helps
if you fix it, let me know what you found... you got me wondering now...
jay
